docs: def to_tnw(orbit):
      """In the TNW Local Orbital Reference Frame, x is oriented along the velocity vector,
      z along the angular momentum, and y complete the frame.
  
      Args:
          orbit (list): Array of length 6
      Return:
          numpy.ndarray: matrix to convert from inertial frame to TNW.
  
      >>> delta_tnw = [1, 0, 0]
      >>> p = [-6142438.668, 3492467.560, -25767.25680]
      >>> v = [505.8479685, 942.7809215, 7435.922231]
      >>> pv = p + v
      >>> mat = to_tnw(pv).T
      >>> delta_inert = mat @ delta_tnw
      >>> all(delta_inert == v / norm(v))
      True
      """
  
      pos, vel = _split(orbit)
  
      t = vel / norm(vel)
      w = np.cross(pos, vel) / (norm(pos) * norm(vel))
      n = np.cross(w, t)
  
      return np.array([t, n, w])